Chapter 61: Fetal Thorax

What is the best ultrasonic determination for predicting pulmonary hypoplasia?

((chest area- heart area) X 100)/chest area

The mature fetus spends almost ______ of its time breathing

1/3

Pleural fluid is rarely encountered before the

15th week of gestation EXCEPT in association with Down or Turners syndrome

Fetal breathing movements are considered absent if no such fetal activity is noted during the ______ minute observation period

20

When does progressive flattening of the epithelial cells lining the air spaces, which allows closer apposition of capillaries to the fluid-filled air space lumen and results in further development of the air-blood barrier necessary for efficient gas exchange after birth occur?

After 24 weeks

When does a dramatic increase in the number and complexity of air spaces and vascular structures occur?

Between 16-24 weeks

______ may be used to detect fetal breathing through the nostrils

Color flow Doppler

What is a consistent method of diagnosing pulmonary hypoplasia?

a decreased ratio of lung weight to body weight

The thorax is normally slightly smaller than the

abdominal cavity

Bronchogenic cysts occur as a result of

abnormal budding of the foregut

What is the single most important determinant of fetal viability?

adequacy of pulmonary development

What is pleural effusion?

an accumulation of fluid within the pleural cavity that may appear as an isolated lesion or secondary to multiple fetal anomalies

What may the fetus have if they have a significant narrow diameter of the chest?

asphxiating thoracic dystrophy

When does the gut move back into the abdominal cavity?

between 10-12 weeks

When does the normal number of bronchi form?

between 16-20 weeks

When does the muscular diaphragm form?

between 6-14 weeks of gestation

CCAM may communicate with the

bronchial tree

What is the most common lung cyst detected prenatally?

bronchogenic cyst

CCAM is one of the

bronchopulmonary foregut malformations

Abnormal position of the heart may indicate the presence of a

chest mass, pleural effusion, cardiac malformation

What is the most common reason for a pleural effusion?

chylothorax

What forms the upper margins of the thoracic cavity?

clavicles

The ratio of thoracic circumference to abdominal circumference remains _____ throughout the pregnancy

constant

Normal sonographic findings of diaphragm

curvilinear hypoechoic structure coursing anteriorly to posterioly

What does pulmonary hypoplasia result in

decrease in organ size and weight

Pulmonary hypoplasia is caused by a

decrease in the numbers of lung cells, airways, and alveoli

What is the most posterior aspect of the diaphragm?

derived from body wall

The base of the heart lies horizontal to the

diaphragm

What forms the lower margins of the thoracic cavity?

diaphragm

What separates the thoracic cavity from the abdomen?

diaphragm

Lung cysts

echo free masses that replace normal lung parenchyma

Sonographic appearance of pleural effusion

echo-free peripheral masses on one or both sides of the fetal heart effusions conform to the thoracic cavity and often compress lung tissue lung appears to float in the fluid

Sonographic findings of congenital bronchial atresia

echogenic pulmonary mass lesion

Sonographic findings of pulmonary sequestration

echogenic solid mass resembling lung tissue rarely occurs below diaphragm normal intraabdominal anatomy

Sonographic appearance of diaphragm

echogenic, smooth hypoechoic muscular margin between the fetal liver or spleen and the lungs

What causes CCAM?

embryogenetic alteration in the developing lung during the first 8-9 gestational weeks

Normally, the primitive diaphragm is intact by the

end of 8th menstrual week

Which has a poorer prognosis, intralobar or extralobar sequestration?

extralobar- bc of associated anomalies and hydrops

CCAM type 2 lesions are associated with

fetal and/or chromosomal abnormalities in 25% of cases (renal agencies, pulmonary anomalies, diaphragmatic hernia)

A small percentage of infants have pulmonary hypoplasia with no

fetal or uterine problem

What should be seen caudal to the diaphragm?

fetal stomach and liver

What chain of events forms the diaphragm?

fusion of the septum transversum, pleuroperitoneal membranes, dorsal mesentery of the esophagus and body wall

Prognosis of pulmonary hypoplasia

grave 80% die after birth

The lungs at birth are about _____ with fluid derived from the amniotic cavity, tracheal glands and lungs

half full

The lungs serve as the lateral borders for the

heart

Congenital diaphragmatic hernia (CDH)

herniation of the abdominal viscera into the chest that results from a congenital defect in the fetal diaphragm

Texture of fetal lungs

homogeneous with moderate echogenicity

What often accompanies chylothorax?

hydramnios- resulting from esophageal compression

What is pulmonary sequestration associated with?

hydrops and polyhydramnios, diaphragmatic hernia, gastrointestinal anomalies

Pleural effusion AKA

hydrothorax

Pleural effusions may result from

immune or nonimmune causes congestive heart failure chromosomal abnormalities cardiac masses

What results in lethal pulmonary hypoplasia?

kidney abnormalities IUGR PROM

Congenital bronchial atresia is found most commonly in the

left upper lobe

Early in gestation, the lungs are similar to or slightly less echogenic than the

liver

Congenital lobar emphysema

lobar overinflation of the lung without destruction of alveolar septa

Ultrasound can NOT be used to assess

lung maturity

What should be seen cephalad to the diaphragm?

lungs and heart

CCAM type 2

macro cystic with a microcytic component lesions consist of multiple small cysts < 1 cm

CCAM type 1

macrocystic one or more large cysts replace normal lung tissue > 2 cm, up to 10 cm

What may also cause pulmonary hypoplasia?

masses within the thoracic cavity

The presence of a pleural effusion may cause a shift in

mediastinal structures, compression of the heart, and inversion of the diaphragm

The central portion of the thorax is occupied by the

mediastinum

CCAM type 3

microcystic malformations are characterized as bulky, large, non cystic lesions appearing as echo-dense masses of the entire lung lobe

Congenital lobar emphysema may appear identical to

microcystic CCAM- presenting as large solid mass

Most of the heart is positioned in the

midline and left chest

Prognosis of pleural effusion

mortality rate: 50% prognosis is poor with associated hydrops

What part of the diaphragm forms last?

most posterior aspect

What is the most commonly defective part of diaphragm?

most posterior aspect, derived from body wall

Congenital cystic adenomatoid malformation (CCAM)

multi cystic mass within the lung consisting of primitive lung tissue and abnormal bronchial and bronchiolar-like structures

This extra lung tissue is

nonfunctional

Pulmonary hypoplasia commonly occurs after prolonged

oligohydramnios or secondary to a small thoracic cavity caused by a structural or chromosomal abnormality

Type 2 and 3 have

poorer prognosis associated polyhydramnios and anasarca have poor prognosis

Compression of lung parenchyma may cause

pulmonary hypoplasia

In the presence of oligohydramnios what may be present?

pulmonary hypoplasia with a reduction in overall thoracic size

What is the major reason why fetuses younger than 24 weeks of gestation are generally considered nonviable?

pulmonary immaturity

Unilateral pulmonary agenesis or hypolasia

rare anomaly often associated with other fetal malformations

Congenital bronchial atresia

rare pulmonary anomaly that results from the focal obliteration of a segment of the bronchial lumen

What forms the lateral margins of the thoracic cavity?

ribs

When fetal hydrothorax is bilateral, it occurs about equally on the

right and left sides

Chylothorax

right-side unilateral collection of fluid secondary to a malformed thoracic duct

Fetal breathing becomes more prominent in the

second and third trimesters

Fetal breathing movements are documented if characteristic ______ movements of the fetal chest or abdomen are sustained for at least 20 seconds

seesaw

What does pulmonary sequestration develop from?

separate outpouching of the foregut or by separation of a segment of the developing lung from from the tracheobronchial tree

Sonographic findings of bronchogenic cysts

small circumscribed masses with no evidence of a mediastinal shift or heart failure AFV is normal

Fetal respiration is decreased by the mother

smoking

The apex of the heart should be directed toward the

spleen

Fetal respiration is stimulated by mothers increased

sugar doses

The lungs lie _____ to the diaphragm

superior

Pulmonary sequestration

supernumerary lobe of the lung, separated from the normal tracheobronchial tree extra pulmonary tissue is present wihin the pleural lung sac (intralobar) or is connected to the inferior border of the lung within its own pleural sac (extra lobar)

Thoracic cavity look

symmetrically bell shaped

Where does the extra lung tissue get its blood supply from?

systemic circulation

What is associated with asphyxiating thoracic dystrophy?

thanatophoric dwarfism

Where does the extra lung tissue get its arterial supply from?

thoracic aorta, with venous drainage into the vena cava

The fluid present in the lungs at birth clears by 3 routes:

through the mouth and nose into the pulmonary capillaries into the lymphatics and the pulmonary vessels

Bronchogenic cysts lack any communication with the

trachea or bronchial tree

At what level in the chest circumference leveled at?

transverse plane at the level of the four chamber view of the heart

Most CCAM lesions are

unilateral and do not favor either lung

Fetal hydrothorax can be

unilateral or bilateral

Congenital lobar emphysema usually occurs in the

upper left or middle lobe and is located within the normal pleural envelope

Where does bronchogenic cysts usually occur?

within the mediastinum or lung